Trouble hot starting 93 r1 low miles good compression
 

Okay so I recently acquired a beautiful stock r1 93 rx7 and previous owner had a hard time starting it etc getting it to run idle etc.

so I replaced some vacuum lines, many were old hard cracked maybe and broken solenoids plastics etc. I replaced them w new check valves and solenoids (broken nipple ones)

put new plugs and plug wires in.

starts up great cold. It goes up to 2500 rpm though about 5-10 seconds. and falls down to 1500 rpm and hovers for a while and Slowly drops and while driving idles around 700 rpm.

before all of this I had the compression checked and the mechanic said great numbers. both rotors were between 107-115

it almost seems like a tuning issue with the injectors, throttle or something. Low rpm off the light throttle is a little shakey but other than that not too bad.

any idea where to look? I’ll put some injector cleaner in and see if that will do anything.

thanks guys maybe I’ll try to take some video of it and post it up as well if I can

So I took it to Toyota 😅 dealer (my friend works there) and they inspect cars for free.

put it on the lift and there were oil residual as it was caked on from the past. Some coolant leak but little bit I think it’s from the radiator hose and clamp.

but anyway they added some fuel cleaner in the gas tank . And it seemed to help the hot start issue! It was only restarted twice in hot tonight. But both times fired up a lot better than prior to putting in the fuel cleaner.
I also just got a new Mazda fuel filter I’ll be replacing tmrw. We will see hopefully that cures it??

interesting...

also I noticed this downpipe thats on here one of the stud is missing w the nut of course. But the angle of the pipe seems like it’s really hard to put a stud and any nut on! Is this common w most down pipes??
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Ok so even after the fuel cleaner from Toyota it seemed to help a little bit... but still had that hot start issue.

well today I replaced the stock fuel filter w a new oem one. What a pita on jack stands! Lol

I drove around for a while after and tried to restart it multiple times hit restart and each time I fired up good! So fingers crossed that fixed it...

it’s idling a little bit low sometime or at least it drops down into 500s sometime (mostly it’s between 800-900). Is there away to increase the idle a little higher? Maybe 900-1000?

because seems like from a real low rpm idle stop to initial tip in of the throttle, sometime it bucks and isn’t the smoothest with take offs. I’m being pretty anal though. Not sure if it’s ok and or common to do that?

i just read and learned of why my car jumps up to 2500+ rpm initial cold start! Because in neutral it will do that but i learned if we start it in first gear clutch in, then it only goes to 1500rpm! 👍😁

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Seems like you are on the right track. If the compression is indeed good, and you can't find anything else obvious, pull the injectors and have them cleaned and tested.

How are those spark plugs looking?

Also, don't trip too hard on the oil leak. These cars are infamous for leaky oil pans. You can get a new one for pretty cheap but they're kind of a bitch to replace.

Haven’t checked the plugs since I put the new ones in and did those vacuum hoses repair.

as for the high idle I just found out that if you start cold in neutral, it will go into higher idle mode..?
vs start it in gear and it goes to 1500 rpm instead of 2500

do you guys know if the car is hotter or low on coolant if it will affect hot restarts?

If you have good compression, you should not have hot starting problems.

So I had the hot start issue again tonight but this was probably the worst since I got the car back up and thought I fixed it!

what I do notice is I think it is coolant related? Is there a coolant sensor that could go bad or?

when drive and let it sit maybe for a few min it has a hard time starting. If I drive and I turn it off and turn it back on right after I shut it off, it will restart. Only when it sits for a couple min.

crank crank and after cooling off for a little while. I feather and modulate the throttle. It barely catches and the throttle feels really off. Like I have it WOT but the rpm is barely Going up struggling. And finally if and when it catches, it sounds like it’s misfiring and not firing on all cylinders cleanly. When i get the rpm to go up past 2k rpm then it clears away and car Sounds and idles okay again.

also seems like I’m losing coolant decently quick. Which is not a good sign? I’ll have to check for exterior leaks (I thought I saw it on the radiator hose/clamp)

any ideas? I thought changing out the fuel filter cleared it away but not that lucky 😑
gotta keep ruling stuff out!

Here’s a quick video the morning after the hot start issue.
cold start here, fired right up but ignition and or fuel sounds really rough.


this is a bone stock fd not modded so shouldn’t sound aggressive :)

after less than 30 sec it seemed like it cleared away. Similar to last night. Like the ecu or engine needed to catch up and once it cleared it drove and ran fine.

seems like a tuning issue?? I smelled a little bit of coolant On start up and I think I’m losing coolant (somewhere).

thanks for any feedbacks

If you smell coolant out of the exhaust then that would explain your issue. Coolant getting in the combustion chamber and "flooding" that rotor, engine cranks over long enough and clears it out.

would that be some type of seal or engine issue? Compression read 107-115 on all the rotors recently.
but ya that could make sense. After driving a bit the coolant goes in the engine and floods it. But when it’s cold it hasn’t flooded so it will fire right up?

if that’s the case what would the fix be?

:goodrebuild:

😬😩😭

Stuck injectors maybe. I've had similar situations when an injector gets stuck open when its hot so it floods the housings. Then the fuel would evaporate after a little time passes and the car would fire right up. Look into that

This right here.. I would check averything before considering a rebuild though.

The concerning part is that you are losing coolant and you can smell it.

Yes I will def check everything and it still can be fuel related you guys are right. Because as soon as I put in some fuel cleaner it helped. And also after I changed the fuel filter that helped also. But I gotta see where and how much coolant I’m missing as well. At least it starts back up after sitting for a little bit and clears up even if it has some issue unlike before the previous owner said it wouldn’t start for weeks etc..

Fill the coolant back up and perform a champagne test. Search the forum for it, but it’s basically letting the car run with the radiator fill cap open and looking for tiny bubbles that resemble champagne bubbles.
If the coolant seal is comprised the compression from the housings can go into the cooling system and cause the air bubbles l.

I wouldn’t assume rebuild without those compression numbers

Ok did a quick champagne bubble test. Hope I did it right? But There were bubbles coming out... also I saw what looks like the radiator hose leaking also bubble?
I also checked the Supra and no bubbles.. ehh

ill take off the radiator hoses and check them first..

Signs of a blown coolant seal:
- Bubbles in your coolant
- White exhaust smoke
- Wet plugs
- Overflowing coolant overflow tank

If you want to be positive, give it a pressure test (need to make sure first you have no coolant leaks like your radiator hose)

Thank you

so I took one of the radiator hose off (the one that looked like it was leaking). And I found this. It’s cracked by the coupler.. not sure if this will cause a big leak or not..? And I don’t know if it’s reusable if I trim the broken part off and re-attach?
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Fix that hose and redo the champagne test, that’s not looking good though unfortunately.

So I fixed the radiator hose and put it back together. Did a quick champagne test and yes it still had air bubbles a lot. Maybe more so now...

I’ll try to drive it around and see if it still runs into those hot start issues again...

I added some marvel mystery oil in the gas mix to see if it helps clean out the injectors or whatever

I’ll try to rent a test kit for combustion gas in the coolant.. I think oreillys or autozone rents kits out.

i don’t really see any signs of white smoke much tho upon start up cold or hot or while driving.
And I let it warm up shut it off and it started back up fine every time tonight. But I didn’t drive it I just kept it idling

Silicone tears. Use OEM hoses

A rotary will work with a small leak, but you want to address it sooner than later. Waiting too long, the water starts rusting the internals and eventually it will progressively get worse to the point of having too much water to fire.